Illustratively, such a packing is known from the European patent document, A 0 046 894. The insert material of this packing consists of closed-pore foam particles in bulk which cannot fully absorb the heat-or cold-storing liquid. These foam particles are polystyrene spheres which, in this shape, are easily displaced relative to one another. They are 1 to 5 mm in diameter, especially 4 to 5 mm, and are temperature-insensitive. A packing filled with spheres allows excellent molding to specific body sites.
However, it has been found in practice that the need for molding capability precludes tautly filling the packing with spheres; thus, these spheres disclosed in EP A 0 046 894 can move so much within the packing casing that they may concentrate in one part of it whereas no plastic spheres are present in the other part of the pouch-shaped packing. In fact, this is desirable to the extent that the packing lies horizontally on a body part because then the foam particles will buoy at the side away from the body and form an insulating layer. However, when the packing is not applied horizontally, this buoyancy causes the foam particles to concentrate at one end of the packing and, as a result, undesirable, uneven thermal behavior is incurred over the area of the packing.
The displacement of the spheres into one part of the packing takes place when the packing is stored, not (surface) prone, but standing on one edge. Deliberate, thorough mixing of the packing contents is quite different.
Moreover, the foam spheres fill a large part of the packing volume. However, the spheres cannot store heat; that is, only the liquid assures heat storage, but this liquid takes up only somewhat than half the packing volume for a commercial packing made in the manner of the patent application. In order to absorb or dissipate as much heat as other packings, such a packing must be made about twice as thick.
The European patent document A 0 046 894 further describes a pouch-shaped packing which is assumed already known in that text, in which the insert material consists of an integral and essentially planar foam absorbing the liquid. Essentially, this foam serves to assure uniform thickness of the packing because the two sheets of the pouch-like packing rest on this foam over the entire packing area once the liquid has been substantially absorbed by the foam.
However, such packing is not easily molded, that is, matching to the body surface is limited. Also, temperature loss is unhampered and frequently high and rapid heat transfer takes place, i.e., the body part is excessively cooled or heated, such effects on one hand decaying too rapidly and on the other hand, they may entail undesired phenomena such as frostbites or burns.